Film of allyloxy compound with metal drier compositions

ABSTRACT

Metal drier moderated to provide compostions of extended pot life by at least one molybdenum compound. Coating compositions of free radical polymerizable compounds and moderated metal drier exhibit lower propensity to yellowing when they are cured.

This is a division, of application Ser. No. 049,573, filed May 13, 1987now U.S. Pat. No. 4,810,757.

This invention relates to metal drier catalyst compositions and inparticular to metal drier catalyst compositions moderated in theiractivity by molybdenum compounds.

Surface coatings of free radical-polymerizable compounds are preferablycured with an activator or crosslinker to provide a durable coating.Such curing is often promoted by use of a metal drier, e.g. a cobalt ormanganese compound, and a free radical initiator, e.g. a peroxide. Suchmetal driers enhance the curing by allowing rapid (e.g. less than about1 hour) curing to tough, tack free films at low temperatures (e.g. lessthan 100 C.) A disadvantage is that coating compositions comprisingdesirable metal driers such as cobalt compounds and peroxides haveundesirably short pot life, e.g. often less than about an hour or so. Asdisclosed in copending applications Ser. No. 946,740 now U.S. Pat. No.4,778,864 and 946,742, now U.S. Pat. No. 4,816,535 both filed Dec. 24,1986, extended pot life, e.g. at least about 8 hours or more, has beenprovided with coating compositions comprising a temporary catalystinhibitor, e.g. a strong fugitive acid such as trifluoroacetic acid.

Such fugitive said stabilized compositions provide tough, durablecoatings. In certain applications, e.g. when applied as clear coatingsover white surfaces or as white pigmented coatings, such coatings whichretain the dispersed metal drier are prone to undesirable discoloration,e.g. yellowing. The generation of color can be reduced by replacing thecobalt compound which allows curing at moderate temperature, e.g. atabout 50° C., with a less active metal drier, e.g. a molybdenumcompound, which requires undesirably higher temperatures, e.g. about100° C., and/or longer time to effect curing.

An object of this invention is to provide a moderated metal driercatalyst which exhibits the desirable characteristics of cobaltcompounds such as rapid cure at low temperature, but which has asubstantially extended pot life and provides coatings with enhancedresistance to discoloration.

SUMMARY OF THE INVENTION

It has been discovered that certain soluble molybdenum compounds can beutilized to attenuate the activity of metal driers in coatingcompositions to provide extended pot life and discoloration-resistantcoatings. Accordingly, this invention provides novel free radicalpolymerization catalysts comprising metal driers and at least one ofsaid compounds which have a solubility in methyl ethyl ketone, ethanolor toluene of at least 0.1% by weight. This invention also providescoating compositions comprising a free radical-polymerizable compound,an allyloxy compound, and a free radical initiator together with suchcatalyst which provides the composition with an extended pot life andallows the composition to be cured to tough coatings that are resistantto discoloration. Also provided are methods of making and using suchcatalysts and coating compositions.

DESCRIPTION OF PREFERRED EMBODIMENTS

The free radical polymerization catalyst of this invention comprises ametal drier and at least one molybdenum compound wherein said compoundhas a solubility in methyl ethyl ketone, ethanol or toluene of at least0.1% by weight. Metal driers are well known in the coating industry andpreferred metal driers often include cobalt and manganese compounds,e.g. fatty acid salts of such metals. In many cases preferred metaldriers include cobaltous acetate, citrate, acetyl-acetonate,2-ethylhexanoate, and the like. Metal driers are typically provided incoating compositions at catalytically effective levels of from about0.001% to about 1% by weight.

In the catalyst of this invention the metal drier is effectivelymoderated to provide coating compositions of enhanced pot life by theinteraction of a soluble molybdenum compound, preferably a molybdenum(VI) compound. Such compounds are desirably soluble in a solventmiscible with the coating composition, e.g. methyl ethyl ketone, ethanolor toluene. Preferred molybdenum compounds comprise molybdenum dioxidedichloride, phosphomolybdic acid, or more preferably molybdenum dioxidebis(2,4-pentanedione). The 2,4-pentanedione ligand is commonly calledacetyl-acetonoate and is hereinafter referred to by its commonabbreviation, i.e. "Ac-Ac". When used in coating compositions enhancedpot life and discoloration resistance is achieved when the molar ratioof molybdenum to metal of the drier, e.g. cobalt, is about 0.1 to 10,for instance about equimolar ratios. Although it has been found thathalogenated compounds are among those useful in extending pot life andreducing the tendency toward discoloration, e.g. by action of the metaldrier, it is nonetheless preferred to avoid such halogenated compoundswhich may be involved in different discoloration mechanisms, e.g. photoactive discoloration.

The catalysts of this invention can be prepared by mixing solutions ofmetal drier and molybdenum compound. When such catalysts are provided incoating compositions, it is generally desirable to add the catalyst asthe last component of the composition. When the moderated catalyst hasnot been previously prepared, it is desirable to first add themolybdenum compound to the coating composition, followed by the metaldrier to minimize any premature curing by extremely active metal driersuch as cobalt compounds.

The moderated catalyst of this invention can be used to promote the freeradical polymerization of a variety of compositions, e.g. coatingcompositions comprising free radical polymerizable compounds andallyloxy compounds, including compositions comprising free radicalinitiators.

Such free radical initiator can comprise peroxides such as t-butylhydroperoxide, cumene peroxide, methyl ethyl ketone peroxide, lauroylperoxide, benzoyl peroxide, azo-bis(isobutyronitrile) and the like andmixtures thereof.

The free radical-polymerizable compound useful in the composition andmethods of this invention can be an unsatured monomer or oligomer ormixture of monomers and oligomers. The nature of the compound is notcritical so long as it is activated towards free radical polymerizationvia the double bonds when it is brought into reactive admixture with ametal drier and/or free-radical initiator. Such compounds include dryingoils such as castor, linseed, oticica, safflower, soybean, sunflower,tung and certain fish oils; acrylic monomers; vinyl monomers such asstyrenic monomers, vinyl ethers, vinyl esters, vinyl imides, vinylamides; maleates and fumarates. In many cases it is preferred that suchcompounds be selected from acrylyl monomers or oligomers; such preferredcompounds desirably having a number average molecular weight less thanabout 4000 and contain from 1 to about 10 unsaturated groups permolecule. A particularly preferred group of acrylyl monomers isrepresented by the structure: ##STR1## where R₁ is selected from thegroup consisting of H, CH₃ and C₂ H₅, where is an integer in the rangeof 1 to 10 and Z is a saturated or ethylenically unsaturated residue ofan alcohol or polyol, a carboxylic acid or poly carboxylic acid, anamine or a polyamine, an epoxide or polyepoxide or an isocyanate orpolyisocyanate of a number average molecular weight less than about 4000containing a hydrocarbon, ester, amide, ether or urethane backbone. Suchmonomers may be obtained by reaction of acryloyl, methacryloyl orethacryloyl chloride with an alcohol, a polyol, an amine, or a polyamineor by the reaction of acrylic acid, methacrylic acid or ethacrylic acidwith an epoxide, a polyepoxide, an isocyanate, or a polyisocyanate, orby reaction of a hydroxyalkyl acrylate, methacrylate or ethacrylate witha carboxylic acid, polycarboxylic acid, an epoxide, a polyepoxide, anisocyanate, or a polyisocyanate. Such monomers include methyl acrylate,methyl methacrylate, butyl acrylate, 1,3-butylene glycol diacrylate,1,6-hexanediol diacrylate, the polyacrylates, polymethacrylates andpolyethacrylates of polyethylene glycols and polyols, polypropyleneglycols and polyols and poly(tetramethylene glycols) andpoly(tetramethylene) polyols of molecular weight in the range of 100 to4000, pentaerythritol tetracrylate, trimethylolpropane triacrylate,dipentaerythritol monohydroxypentacrylate, ethoxylated bisphenol Adimethacrylate, the diacrylates, dimethacrylates and diethacrylates ofepoxy compounds formed from bisphenol A and epichlorohydrin of molecularweight in the range of 200 to 4000, and the polyacryloyl monomersprepared by reacting isocyanate capped polyethers and isocyanate cappedpolyesters of molecular weight up to 4000 with hydroxyethyl acrylate.

The coating compositions and methods of this invention also comprise anallyloxy compound which may tend to activate the cure process. Certainallyloxy compounds can advantageously serve as crosslinking agents toprovide desirable cured film properties. Suitable allyloxy compounds areselected from β, γ-unsaturated ethers having at least one α-hydrogenatom in which the allyloxy group may be represented by the followingformula: ##STR2## The β, γ-unsaturated ether compound has an equivalencyless than about 300, based upon the number of β, γ-unsaturated ethergroups having an α-hydrogen, a molecular weight less than about 10,000,and has from 1 to 60 β, 65-unsaturated ether groups.

The allyloxy compounds are generally aliphatic in character.Alternatively, compounds having β, γ-unsaturation with a triple bond asin propargyl methyl ether, dipropargyl ether, tripropargyl trimethylolpropane, or hexapropargyl sorbitol may be used and are consideredequivalent to allyloxy compounds for purposes of this invention.Exemplary of allyloxy compounds useful in the compositions of thisinvention are the following: methyl allyl ether, methyl methallyl ether,butyl allyl ether, diallyl ether, allyl methallyl ether, dicrotyl etherdi-(2-chloro-2-propenyl) ether, di-(2-phenyl-2-propenyl) ether,di(1-methyl-2-propenyl) ether, 1-phenyl-2-propenyl ether,di-(3-phenyl-2-propenyl) ether, di-(2-isopropyl-2-propenyl) ether,1,4-diallyl oxy-2-butene, 1,4-diallyloxy-2-butyne, 1,6-diallyloxyhexane, 1,4-dimethallyloxypentane, 2,5-dimethoxy-2,5-dihydrofuran,allyl glycidyl ether; allyloxy compounds prepared from the ionicpolymerization of allyloxyalkyl acrylates, methacrylates, acrylamides orthe allyloxy derivatives of vinyl ethers, such aspoly(allyloxyethylmethacrylate) and poly(allyl vinyl ether); allyloxycompounds wherein the allyloxy group forms part of an oligomericbackbone, such as poly(2-buten-1,4-diol) or 2,5-poly(2,5-dihydrofuran).

Preferred allyloxy compounds may be selected from the group ofpolyethers and polyesters represented by the structural formula:##STR3## where R₂ is a radical of molecular weight less than about10,000 obtained by removal of active hydrogen from an active hydrogencompound selected from the group consisting of water, alcohols, thiols,carboxylic acids, carboxylic amides and amines, where the functionalityof R₂ is n and is in the range of 1 to 10, where E is a divalent radicalselected from the group represented by the formulae ##STR4## where the Xgroups are independently selected from the group consisting of H, CH₃,C₂ H₅ and CH₂ OCH₂ Y, Y being selected from the group consisting ofCH═CH₂, H₃ C--C═CH₂, and H₅ C₂ --C═CH₂, where a is 0 or 1, where R₃ ishydrogen or an unsubstituted or substituted C₁ to C₁₀ hydrocarbylradical, where R₄ is a divalent unsubstituted or substituted C₂ to C₁₀hydrocarbyl radical and where the product of m and n is at least 4 andnot more than about 60. It is anticipated that any of the hydrogens inY, except at least one alpha to the ether group, can be replaced with alower alkyl without substantially affecting the invention and that theresulting compounds would be equivalent to those according to theinvention. Polyethers containing an allyloxy group may be prepared byionic polymerization of allyl glycidyl ether or mixtures of allylglycidyl ether and the appropriate alkylene oxide and polyesterscontaining an allyloxy group may be prepared by polymerization of asuitable dicarboxylic acid and the monoallyl ether of glycerol. Suitablepolyesters may also be prepared by substituting for the monoallyl etherof glycerol, the monoallyl ether of trimethylolethane, themonoallylether of trimethylolpropane, the monoallyl ether ofpentaerythritol, the diallyl ether of pentaerythritol and similar monoand polyallyl ethers of polyols. Allyl glycidyl ether or methallylglycidyl ether may also be substituted for the monoallyl ether ofglycerol.

Another group of preferred allyloxy compounds is represented by thestructural formula:

    R.sub.5 (OCH.sub.2 Y).sub.p

where R₅ is a C₂ to C₁₂ aliphatic hydrocarbyl or oxahydrocarbyl radicalof equivalence p in the range of 2 to 12 and Y is a group as definedhereinabove. Such compounds include tetrallyl pentaerythritol, hexaalyldipentaerythritol, hexallyl sorbitol, hexamethallyl mannitol,tetraallyl-β-methyl glucoside, and decaallyl sucrose.

Yet another group of preferred allyloxy compounds are acetals derivedfrom allyl alcohol or methallyl alcohol and aldehydes and those derivedfrom a polyol and an acrolein compound represented by the structuralformulas:

    R.sub.6 (CH(OCH.sub.2 Y).sub.2).sub.q

    and

    R.sub.7 (O.sub.2 CHY).sub.s

where R₆ is absent or is a C₁ to C₂₀ unsubstituted or a substitutedhydrocarbyl group, Y is a group as defined hereinabove and q is in therange of 2 to about 30; and where R₇ is a radical of molecular weightless than about 10,000 obtained by removal of at least two activehydrogens from a polyol and r is in the range of about 1 to about 170.Such compounds include 1,1,2,2-tetrakis(allyloxy)ethane,1,1,6,6-tetrakis(allyloxy)hexane and those derived from acrolein,methacrolein or crotonaldehyde and a polyol and those derived frompolyacrolein and acrolein copolymers. Exemplary are triallylidinesorbitol and the polyacrolein acetal of polyvinyl alcohol.

The more preferred allyloxy activator compounds are the polyether andpolyacetal compounds in which the number of allyloxy groups per averagemolecule is in the range of 2 to 40 and the allyloxy equivalent is lessthan about 250. Most preferably the allyloxy equivalent is less thanabout 150.

The compositions and methods also utilize a free radical initiator. Suchfree radical initiator can comprise peroxides such as t-butylhydroperoxide, cumene peroxide, methyl ethyl ketone peroxide, lauroylperoxide, benzoyl peroxide, azo-bis(isobutyronitrile) and the like andmixtures thereof.

Depending on the end use and the application requirements it may beconvenient to add any of the other conventional additives for surfacecoating compositions such as solvents, pigments, fillers, reinforcingagents, stabilizers, inhibitors and flow control agents. The proportionsof the ingredients can vary widely depending on the compatibility of themajor ingredients and the nature of the coating to be obtained. Themajor ingredients are advantageously selected to be compatible with oneanother to provide a sufficiently rapid cure of the coating and to avoidimpairment of gloss and clarity of the cured coatings. Compatibility isreadily determined by mixing the major ingredients and determining therange of mixtures which do not form cloudy solutions or coatings orseparate into phases. Provided that the major ingredients are suitablycompatible, a weight range of allyloxy compound tofree-radical-polymerizable compound (e.g. in the range of from 70:30 to1:99) can be used. Preferably this ratio will be in the range from 40:60to 5:95 to provide an adequate rate of cure and an adequate level ofmechanical properties in the cured coating.

In those cases where it may be desirable to provide solvent (or vehicle)for the coating composition of this invention, such solvent ispreferably a volatile organic compound comprising a ketone, such asacetone, methyl ethyl ketone, methyl isobutyl ketone, etc.; an estersuch as ethylene glycol monoethyl ether acetate; an aromatic such astoluene, xylene; or a mixture thereof.

The coating compositions of this invention are advantageously applied asthin films to substrates. Such films are generally cured by heating thefilm, e.g. in an air oven or by IR lamps, to accelerate cure to a tough,solvent-resistant coating. Exposing the film to a temperature of up toabout 100° C., say between about 50° C. and 80° C., provides quiteacceptable cured films. Higher temperatures can of course be utilizedespecially to effect curing in shorter times.

The following disclosure is provided to illustrate specific embodimentsand aspects of this invention but does not imply any limitation of thescope of the invention.

MATERIALS USED

In the following described materials, the symbol "(n)" indicates asolution in the identified solvent where "n" is the weight percent ofthe described material in solution.

UVl(n): acrylated urethane oligomer obtained from Morton-Thiokol Companyas Uvithane-893, unsaturation 0.15-0.175 equivalents/100 g; diluted withMEK to provide a solution of weight percent indicated in parenthesis,e.g. UVI(75) is 75 wt.%.

AOC: allyloxy compound, a reaction product of ethylene glycol and allylglycidyl ether (1:10 mole ratio) in the presence of borontrifluoride/etherate catalyst at 75°-80° C. The allyl glycidyl ether isadded over a period of 5 hours. The catalyst is neutralized with NaOHsolution. The aqueous phase is separated from an organic phase productwhich is dried and filtered. The liquid organic product has a Gardnerviscosity of F at 25° C. and an allyloxy equivalent of about 120.

MEK: methyl ethyl ketone

BPO: benzoyl peroxide, 10% solution in MEK.

Co(n): a cobalt catalyst compound obtained from Nuodex, Inc. as Nuocure™10% cobalt catalyst in mineral spirits; solution diluted with MEK toweight percent indicated in parenthesis, e.g. Co(0.1) is 0.1 wt.%cobalt.

Mo(n): a solution of molybdenum (VI) dioxide bis (Ac-Ac) in a mixture ofethanol/methanol (95:5), where the weight percent molybdenum isindicated in parenthesis, e.g. Mo (0.3) is 0.3 wt. % Mo.

BYK: a mar and slip additive obtained from Mallinckrodt, Inc. asBYK-341.

EXAMPLE 1

This example serves to illustrate the effectiveness of a molybdenumcompound, i.e. molybdenum (VI) dioxide bis(Ac-Ac), as acolor-stabilizing, pot life-extending modifier for metal drier, i.e. acobalt compound, in a coating composition according to this invention.

Clear coating compositions were prepared by mixing the components in theorder of their listing in Table 1. "Pot-life", i.e. the time for theviscosity of the composition (about 5 g.) to change from a low level,e.g. similar to water, to a high level, e.g. similar to a non-fluid gel,is measured from the time that the metal drier, i.e. the cobaltcompound, is added to the composition. Films(about 0.13 mm) of eachcomposition are applied over test specimens in accordance with ASTMPractice D3964. "Tack free time" was determined as the time from castingthat the film (maintained at 65) was tack free to the touch.

"Knoop hardness number" (KHN) is determined in accordance with ASTMStandard D 1474 using a Tukon Microhardness Tester (Model 300,Page-Wilson Corp.). "Yellowing Potential", an indication of thepropensity of the film to discolor, is measured as a change in Δb colordifferent over time, where Δb is determined in accordance with ASTMStandard E 805 and D 2244 using a Hunter Lab Color/Difference Meter(D25D2) where the b_(o) standard is -0.7.

                  TABLE 1                                                         ______________________________________                                        COATING COMPOSITIONS                                                          (parts by weight)                                                             Component       A      B        C    D                                        ______________________________________                                        UVI(75)         5.4    5.4      5.4  5.4                                      AOC             1.0    1.0      1.0  1.0                                      BPO             0.5    0.5      0.5  0.5                                      Mo (0.29)       0      0.4      0.8  1.64                                     Co (0.23)       0.22   0.22     0.22 0.22                                     Mo/Co*          0      1.6      3.2  6.4                                      Pot Life (hours)                                                                              2.5    8.2      56   73                                       Tack Free Time, 11     15       18   45                                       (minutes at 65*C)                                                             Hardness, KHN   10     7.7      6.7  3.8                                      Yellowing Potential                                                                           2.9    1.5      1.5  1.2                                      ______________________________________                                         *mole ratio of molybdenum to cobalt.                                     

EXAMPLE 2

This example serves to illustrate the effectiveness of phosphomolybdicacid (1 wt. % in ethanol) in extending the pot life of coatingcompositions.

Clear coating compositions, prepared by mixing components in the orderof their listing in Table 2, were evaluated for pot life. As reportedthe phosphomolybdic acid extended pot life from 4 to 10 hours. Films ofthese compositions dried to tack-free surfaces. The film comprisingphosphomolybdic acid exhibited less propensity to discoloration overtime than the film of the unmodified Composition E.

                  TABLE 2                                                         ______________________________________                                        COATING COMPOSITIONS                                                          (parts by weight)                                                             Component            E      F                                                 ______________________________________                                        UVI (75)             5.3    5.3                                               AOC                  1.0    1.0                                               BPO                  1.5    1.5                                               BYK                  0.06   0.06                                              Phosphomolybdic Acid (1)                                                                           0      0.5                                               Co (0.1)             0.5    0.5                                               Pot Life (hours)     4      10                                                ______________________________________                                    

While specific embodiments of the invention have been described, itshould be apparent to those skilled in the art that variousmodifications thereof can be made without departing from the true spiritand scope of the invention. Accordingly, it is intended that thefollowing claims cover all such modifications within the full inventiveconcept.

What is claimed is: PG,18
 1. A cured film comprising a coating composition comprising:(a) a free radical-polymerizable compound, (b) an allyloxy compound, (c) a metal drier catalyst, (d) a peroxide free radical initiator, and (e) a pot life extending amount of a catalyst modifier comprising at least one molybdenum compound having a solubility in methyl ethyl ketone, ethanol or toluene of at least about 0.1 percent by weight.
 2. The cured film of claim 1 wherein the molar ratio of molybenum to metal drier catalyst is about 0.1 to
 10. 3. The cured film of claim 2 wherein said molybdenum compound is molybdenum dioxide bis(2,4-pentanedione).
 4. The cured film of claim 1 wherein said catalyst is a cobalt compound.
 5. The cured film of claim 2 wherein said metal drier catalyst is cobalt bis(2-ethylhexanoate).
 6. The cured film of claim 2 wherein said free radical-polymerizable compound is of the formula ##STR5## where R₁ is selected from the group consisting of hydrogen, methyl or ethyl, where r is an integer in the range of 2 to 10 and Z is a saturated or ethylenically unsaturated residue of a polyol, a polycarboxylic acid, a polyamine, a polyepoxide or a polyisocyanate of number average molecular weight less than about 2000 containing a hydrocarbon, polyester, polyamide, polyether or polyurethane backbone.
 7. The cured film or claim 6 wherein said allyloxy compound is of the formula

    R.sub.2 ((E).sub.m R.sub.3).sub.n,

    R.sub.5 (OCH.sub.2 Y).sub.p,

    R.sub.6 (CH(OCH.sub.2 Y).sub.2).sub.q,

    and

    R.sub.7 O.sub.2 CHY).sub.s,

where R₂ is a radical of molecular weight less than about 10,000 obtained by removal of active hydrogen from an active hydrogen compound selected from the group consisting of water, alcohols, thiols, carboxylic acids, carboxylic amides and amines, where the functionality of R₂ is n and is in the range of 1 to 10, where E is a divalent radical selected from the group represented by the formula ##STR6## where X is selected from the group consisting of H, CH₃, C₂ H₅ and CH₂ OCH₂ Y,Y being selected from the group consisting of

    CH═CH.sub.2,

    CH.sub.3 --C═CH.sub.2,

    and

    C.sub.2 H.sub.5 --C═CH.sub.2

where a is 0 or 1, where R₃ is hydrogen or an unsubstituted or substituted C₁ to C₁₀ hydrocarbyl radical, where R₄ is a divalent unsubstititued or substituted C₂ C₁₀ hydrocarbyl radical and where the product of m and n is at least 4 and not more than about 60; where R₅ is a C₂ to C₁₂ aliphatic hydrocarbyl or oxahydrocarbyl radical of equivalence p in the range of 2 to 12; where R₆ is absent or is a C₁ or C₂₀ unsubstituted or substituted hydrocarbyl group and q is in the range of 2 to about 30; where R₇ is a radical of molecular weight less than about 10,000 obtained by removal of at least two active hydrogens from a polyol and s is in the range of about 1 to about 170; wherein the weight ratio of α,β-ethylenically unsaturated compound to allyloxy activator compound is in the range of about 30:70 to about 99:1; and wherein the allyloxy compound contains from 4 to 60 allyloxy groups per molecule. 